The agency that people are dealing with in this case is CBP, not TSA. TSA has no border search authority.
We put out the first version of this guide in 2011. So far we don't know for sure if border searches have gotten more prevalent or more intrusive under the Trump administration. It's very possible, but may not be clear from statistics for about a year. They've definitely been getting more press and public attention.
>Border agents cannot deny a U.S. citizen admission to the country. However, if a foreign visitor declines, an agent may deny them entry. If a lawful permanent resident declines, agents may raise complicated questions about their continued status as a resident.
1) comply - possibly incriminating yourself, endangering your security and anyone you have contact with
or
2) refuse, get arrested, harassed, deported and probably placed on some kind of watch list as a known troublemaker
Which should you choose?
The choice is just whether that privacy is more important than getting into America to you.
I don't mean to be churlish but this advice is pretty weak sauce. I mean, I understand why they don't want necessarily want to admit the truth, that if you're a foreign national and you don't comply things will get nasty and you'll almost certainly be deported.
However, that sadly seems to be the truth of Trump's TSA, and if the truth stinks, don't sugar coat it.